CS@CU At ICML 2024

Papers from CS researchers were accepted to the 41st International Conference on Machine Learning (ICML 2024). They join the machine learning research community in Vienna, Austria, on July 21 – 27, 2024. ICML brings together the brightest minds in the field to share their latest findings, foster collaborations, and inspire new directions in machine learning.

The links to the papers and the abstracts are below:

SelfIE: Self-Interpretation of Large Language Model Embeddings
Haozhe Chen Columbia University, Carl Vondrick Columbia University, Chengzhi Mao Columbia University

Abstract:
How do large language models (LLMs) obtain their answers? The ability to explain and control an LLM’s reasoning process is key for reliability, transparency, and future model developments. We propose SelfIE (Self-Interpretation of Embeddings), a framework that enables LLMs to interpret their own embeddings in natural language by leveraging their ability to respond to inquiries about a given passage. Capable of interpreting open-world concepts in the hidden embeddings, SelfIE reveals LLM internal reasoning in cases such as making ethical decisions, internalizing prompt injection, and recalling harmful knowledge. SelfIE’s text descriptions on hidden embeddings open avenues to control LLM reasoning. We propose Supervised Control, which allows editing open-ended concepts while only requiring gradient computation of individual layer. We extend RLHF to hidden embeddings and propose Reinforcement Control that erases harmful knowledge in LLM without supervision targets.

 

Counterfactual Image Editing
Yushu Pan Columbia University, Elias Bareinboim Columbia University

Abstract:
Counterfactual image editing is a challenging task within generative AI. The current literature on the topic focuses primarily on changing individual features while being silent about the causal relationships between features, which are present in the real world. In this paper, we first formalize this task through causal language, modeling the causal relationships between latent generative factors and images through a special type of causal model called augmented structural causal models (ASCMs). Second, we show two fundamental impossibility results: (1) counterfactual editing is impossible from i.i.d. image samples and their corresponding labels alone; (2) also, even when the causal relationships between latent generative factors and images are available, no guarantees regarding the output of the generative model can be provided. Third, we propose a relaxation over this hard problem aiming to approximate the non-identifiable target counterfactual distributions while still preserving features the users care about and that are causally consistent with the true generative model, which we call ctf-consistent estimators. Finally, we develop an efficient algorithm to generate counterfactual image samples leveraging neural causal models.

 

Exploiting Code Symmetries for Learning Program Semantics
Kexin Pei Columbia University, Weichen Li Columbia University, Qirui Jin University of Michigan, Shuyang Liu Huazhong University of Science and Technology, Scott Geng Univerisity of Washington, Lorenzo Cavallaro University College London, Junfeng Yang Columbia University, Suman Jana Columbia University

Abstract:
This paper tackles the challenge of teaching code semantics to Large Language Models (LLMs) for program analysis by incorporating code symmetries into the model architecture. We introduce a group-theoretic framework that defines code symmetries as semantics-preserving transformations, where forming a code symmetry group enables precise and efficient reasoning of code semantics. Our solution, SymC, develops a novel variant of self-attention that is provably equivariant to code symmetries from the permutation group defined over the program dependence graph. SymC obtains superior performance on five program analysis tasks, outperforming state-of-the-art code models, including GPT-4, without any pre-training. Our results suggest that code LLMs that encode the code structural prior via the code symmetry group generalize better and faster.

 

MGit: A Model Versioning and Management System
Wei Hao Columbia University, Daniel Mendoza Stanford University, Rafael Mendes Microsoft Research, Deepak Narayanan NVIDIA, Amar Phanishayee Columbia University, Asaf Cidon Columbia University, Junfeng Yang Columbia University

Abstract:
New ML models are often derived from existing ones (e.g., through fine-tuning, quantization or distillation), forming an ecosystem where models are *related* to each other and can share structure or even parameter values. Managing such a large and evolving ecosystem of model derivatives is challenging. For instance, the overhead of storing all such models is high, and models may inherit bugs from related models, complicating error attribution and debugging. In this paper, we propose a model versioning and management system called MGit that makes it easier to store, test, update, and collaborate on related models. MGit introduces a lineage graph that records the relationships between models, optimizations to efficiently store model parameters, and abstractions over this lineage graph that facilitate model testing, updating and collaboration. We find that MGit works well in practice: MGit is able to reduce model storage footprint by up to 7x. Additionally, in a user study with 20 ML practitioners, users complete a model updating task 3x faster on average with MGit.

 

Position: TrustLLM: Trustworthiness in Large Language Models
Yue Huang Lehigh University, Lichao Sun Lehigh University, Haoran Wang Illinois Institute of Technology, Siyuan Wu CISPA, Qihui Zhang CISPA, Yuan Li University of Cambridge, Chujie Gao CISPA, Yixin Huang Institut Polytechnique de Paris, Wenhan Lyu William & Mary, Yixuan Zhang William & Mary, Xiner Li Texas A&M University, Hanchi Sun Lehigh University, Zhengliang Liu University of Georgia, Yixin Liu Lehigh University, Yijue Wang Samsung Research America, Zhikun Zhang Stanford University, Bertie Vidgen MLCommons, Bhavya Kailkhura Lawrence Livermore National Laboratory, Caiming Xiong Salesforce Research, Chaowei Xiao University of Wisconsin, Madison, Chunyuan Li Microsoft Research, Eric Xing Carnegie Mellon University, Furong Huang University of Maryland, Hao Liu University of California, Berkeley, Heng Ji University of Illinois Urbana-Champaign, Hongyi Wang Rutgers University, Huan Zhang University of Illinois Urbana-Champaign, Huaxiu Yao UNC Chapel Hill, Manolis Kellis Massachusetts Institute of Technology, Marinka Zitnik Harvard University, Meng Jiang University of Notre Dame, Mohit Bansal UNC Chapel Hill, James Zou Stanford University, Jian Pei Duke University, Jian Liu University of Tennessee, Knoxville, Jianfeng Gao Microsoft Research, Jiawei Han  University of Illinois Urbana-Champaign, Jieyu Zhao University of Southern California, Jiliang Tang Michigan State University, Jindong Wang Microsoft Research Asia, Joaquin Vanschoren Eindhoven University of Technology, John Mitchell Drexel University, Kai Shu Illinois Institute of Technology, Kaidi Xu Drexel University, Kai-Wei Chang University of California, Los Angeles, Lifang He Lehigh University, Lifu Huang Virginia Tech, Michael Backes CISPA, Neil Gong Duke University, Philip Yu University of Illinois Chicago, Pin-Yu Chen IBM Research, Quanquan Gu University of California, Los Angeles, Ran Xu Salesforce Research, Rey Ying Yale University, Shuiwang Ji Texas A&M University, Suman Jana Columbia UniversityI, Tianlong Chen UNC Chapel Hill, Tianming Liu University of Georgia, Tianyi Zhou University of Maryland, William Wang University of California, Santa Barbara, Xiang Li Massachusetts General Hospital, Xiangliang Zhang University of Notre Dame, Xiao Wang Northwestern University, Xing Xie Microsoft Research Asia, Xun Chen Samsung Research America, Xuyu Wang Florida International University, Yan Liu University of Southern California, Yanfang Ye University of Notre Dame, Yinzhi Cao Johns Hopkins University, Yong Chen University of Pennsylvania, Yue Zhao University of Southern California

Abstract:
Large language models (LLMs) have gained considerable attention for their excellent natural language processing capabilities. Nonetheless, these LLMs present many challenges, particularly in the realm of trustworthiness. This paper introduces TrustLLM, a comprehensive study of trustworthiness in LLMs, including principles for different dimensions of trustworthiness, established benchmark, evaluation, and analysis of trustworthiness for mainstream LLMs, and discussion of open challenges and future directions. Specifically, we first propose a set of principles for trustworthy LLMs that span eight different dimensions. Based on these principles, we further establish a benchmark across six dimensions including truthfulness, safety, fairness, robustness, privacy, and machine ethics. We then present a study evaluating 16 mainstream LLMs in TrustLLM, consisting of over 30 datasets. Our findings firstly show that in general trustworthiness and capability (i.e., functional effectiveness) are positively related. Secondly, our observations reveal that proprietary LLMs generally outperform most open-source counterparts in terms of trustworthiness, raising concerns about the potential risks of widely accessible open-source LLMs. However, a few open-source LLMs come very close to proprietary ones, suggesting that open-source models can achieve high levels of trustworthiness without additional mechanisms like moderator, offering valuable insights for developers in this field. Thirdly, it is important to note that some LLMs may be overly calibrated towards exhibiting trustworthiness, to the extent that they compromise their utility by mistakenly treating benign prompts as harmful and consequently not responding. Besides these observations, we’ve uncovered key insights into the multifaceted trustworthiness in LLMs. We emphasize the importance of ensuring transparency not only in the models themselves but also in the technologies that underpin trustworthiness. We advocate that the establishment of an AI alliance between industry, academia, the open-source community to foster collaboration is imperative to advance the trustworthiness of LLMs.

 

13 Research Papers Accepted to ICML 2021

Papers from CS researchers have been accepted to the 38th International Conference on Machine Learning (ICML 2021). 

Associate Professor Daniel Hsu was one of the publication chairs of the conference and Assistant Professor Elham Azizi helped organize the 2021 ICML Workshop on Computational Biology. The workshop highlighted how machine learning approaches can be tailored to making both translational and basic scientific discoveries with biological data.

Below are the abstracts and links to the accepted papers.

A Proxy Variable View of Shared Confounding
Yixin Wang Columbia University, David Blei Columbia University

Causal inference from observational data can be biased by unobserved confounders. Confounders—the variables that affect both the treatments and the outcome—induce spurious non-causal correlations between the two. Without additional conditions, unobserved confounders generally make causal quantities hard to identify. In this paper, we focus on the setting where there are many treatments with shared confounding, and we study under what conditions is causal identification possible. The key observation is that we can view subsets of treatments as proxies of the unobserved confounder and identify the intervention distributions of the rest. Moreover, while existing identification formulas for proxy variables involve solving integral equations, we show that one can circumvent the need for such solutions by directly modeling the data. Finally, we extend these results to an expanded class of causal graphs, those with other confounders and selection variables.

 

Unsupervised Representation Learning via Neural Activation Coding
Yookoon Park Columbia University, Sangho Lee Seoul National University, Gunhee Kim Seoul National University, David Blei Columbia University

We present neural activation coding (NAC) as a novel approach for learning deep representations from unlabeled data for downstream applications. We argue that the deep encoder should maximize its nonlinear expressivity on the data for downstream predictors to take full advantage of its representation power. To this end, NAC maximizes the mutual information between activation patterns of the encoder and the data over a noisy communication channel. We show that learning for a noise-robust activation code increases the number of distinct linear regions of ReLU encoders, hence the maximum nonlinear expressivity. More interestingly, NAC learns both continuous and discrete representations of data, which we respectively evaluate on two downstream tasks: (i) linear classification on CIFAR-10 and ImageNet-1K and (ii) nearest neighbor retrieval on CIFAR-10 and FLICKR-25K. Empirical results show that NAC attains better or comparable performance on both tasks over recent baselines including SimCLR and DistillHash. In addition, NAC pretraining provides significant benefits to the training of deep generative models. Our code is available at https://github.com/yookoon/nac.

 

The Logical Options Framework
Brandon Araki MIT, Xiao Li MIT, Kiran Vodrahalli Columbia University, Jonathan DeCastro Toyota Research Institute, Micah Fry MIT Lincoln Laboratory, Daniela Rus MIT CSAIL

Learning composable policies for environments with complex rules and tasks is a challenging problem. We introduce a hierarchical reinforcement learning framework called the Logical Options Framework (LOF) that learns policies that are satisfying, optimal, and composable. LOF efficiently learns policies that satisfy tasks by representing the task as an automaton and integrating it into learning and planning. We provide and prove conditions under which LOF will learn satisfying, optimal policies. And lastly, we show how LOF’s learned policies can be composed to satisfy unseen tasks with only 10-50 retraining steps on our benchmarks. We evaluate LOF on four tasks in discrete and continuous domains, including a 3D pick-and-place environment.

 

Estimating Identifiable Causal Effects on Markov Equivalence Class through Double Machine Learning
Yonghan Jung Columbia University, Jin Tian Columbia University, Elias Bareinboim Columbia University

General methods have been developed for estimating causal effects from observational data under causal assumptions encoded in the form of a causal graph. Most of this literature assumes that the underlying causal graph is completely specified. However, only observational data is available in most practical settings, which means that one can learn at most a Markov equivalence class (MEC) of the underlying causal graph. In this paper, we study the problem of causal estimation from a MEC represented by a partial ancestral graph (PAG), which is learnable from observational data. We develop a general estimator for any identifiable causal effects in a PAG. The result fills a gap for an end-to-end solution to causal inference from observational data to effects estimation. Specifically, we develop a complete identification algorithm that derives an influence function for any identifiable causal effects from PAGs. We then construct a double/debiased machine learning (DML) estimator that is robust to model misspecification and biases in nuisance function estimation, permitting the use of modern machine learning techniques. Simulation results corroborate with the theory.

 

Environment Inference for Invariant Learning 
Elliot Creager University of Toronto, Joern Jacobsen Apple Inc., Richard Zemel Columbia University

Learning models that gracefully handle distribution shifts is central to research on domain generalization, robust optimization, and fairness. A promising formulation is domain-invariant learning, which identifies the key issue of learning which features are domain-specific versus domain-invariant. An important assumption in this area is that the training examples are partitioned into domains'' orenvironments”. Our focus is on the more common setting where such partitions are not provided. We propose EIIL, a general framework for domain-invariant learning that incorporates Environment Inference to directly infer partitions that are maximally informative for downstream Invariant Learning. We show that EIIL outperforms invariant learning methods on the CMNIST benchmark without using environment labels, and significantly outperforms ERM on worst-group performance in the Waterbirds dataset. Finally, we establish connections between EIIL and algorithmic fairness, which enables EIIL to improve accuracy and calibration in a fair prediction problem.

 

SketchEmbedNet: Learning Novel Concepts by Imitating Drawings
Alex Wang University of Toronto, Mengye Ren University of Toronto, Richard Zemel Columbia University

Sketch drawings capture the salient information of visual concepts. Previous work has shown that neural networks are capable of producing sketches of natural objects drawn from a small number of classes. While earlier approaches focus on generation quality or retrieval, we explore properties of image representations learned by training a model to produce sketches of images. We show that this generative, class-agnostic model produces informative embeddings of images from novel examples, classes, and even novel datasets in a few-shot setting. Additionally, we find that these learned representations exhibit interesting structure and compositionality.

 

Universal Template for Few-Shot Dataset Generalization
Eleni Triantafillou University of Toronto, Hugo Larochelle Google Brain, Richard Zemel Columbia University, Vincent Dumoulin Google

Few-shot dataset generalization is a challenging variant of the well-studied few-shot classification problem where a diverse training set of several datasets is given, for the purpose of training an adaptable model that can then learn classes from \emph{new datasets} using only a few examples. To this end, we propose to utilize the diverse training set to construct a \emph{universal template}: a partial model that can define a wide array of dataset-specialized models, by plugging in appropriate components. For each new few-shot classification problem, our approach therefore only requires inferring a small number of parameters to insert into the universal template. We design a separate network that produces an initialization of those parameters for each given task, and we then fine-tune its proposed initialization via a few steps of gradient descent. Our approach is more parameter-efficient, scalable and adaptable compared to previous methods, and achieves the state-of-the-art on the challenging Meta-Dataset benchmark.

 

On Monotonic Linear Interpolation of Neural Network Parameters
James Lucas University of Toronto, Juhan Bae University of Toronto, Michael Zhang University of Toronto, Stanislav Fort Google AI, Richard Zemel Columbia University, Roger Grosse University of Toronto

Linear interpolation between initial neural network parameters and converged parameters after training with stochastic gradient descent (SGD) typically leads to a monotonic decrease in the training objective. This Monotonic Linear Interpolation (MLI) property, first observed by Goodfellow et al. 2014, persists in spite of the non-convex objectives and highly non-linear training dynamics of neural networks. Extending this work, we evaluate several hypotheses for this property that, to our knowledge, have not yet been explored. Using tools from differential geometry, we draw connections between the interpolated paths in function space and the monotonicity of the network — providing sufficient conditions for the MLI property under mean squared error. While the MLI property holds under various settings (e.g., network architectures and learning problems), we show in practice that networks violating the MLI property can be produced systematically, by encouraging the weights to move far from initialization. The MLI property raises important questions about the loss landscape geometry of neural networks and highlights the need to further study their global properties.

 

A Computational Framework For Slang Generation
Zhewei Sun University of Toronto, Richard Zemel Columbia University, Yang Xu University of Toronto

Slang is a common type of informal language, but its flexible nature and paucity of data resources present challenges for existing natural language systems. We take an initial step toward machine generation of slang by developing a framework that models the speaker’s word choice in slang context. Our framework encodes novel slang meaning by relating the conventional and slang senses of a word while incorporating syntactic and contextual knowledge in slang usage. We construct the framework using a combination of probabilistic inference and neural contrastive learning. We perform rigorous evaluations on three slang dictionaries and show that our approach not only outperforms state-of-the-art language models, but also better predicts the historical emergence of slang word usages from 1960s to 2000s. We interpret the proposed models and find that the contrastively learned semantic space is sensitive to the similarities between slang and conventional senses of words. Our work creates opportunities for the automated generation and interpretation of informal language.

 

Wandering Within A World: Online Contextualized Few-Shot Learning
Mengye Ren University of Toronto, Michael Iuzzolino Google Research, Michael Mozer Google Research, Richard Zemel Columbia University

We aim to bridge the gap between typical human and machine-learning environments by extending the standard framework of few-shot learning to an online, continual setting. In this setting, episodes do not have separate training and testing phases, and instead models are evaluated online while learning novel classes. As in the real world, where the presence of spatiotemporal context helps us retrieve learned skills in the past, our online few-shot learning setting also features an underlying context that changes throughout time. Object classes are correlated within a context and inferring the correct context can lead to better performance. Building upon this setting, we propose a new few-shot learning dataset based on large scale indoor imagery that mimics the visual experience of an agent wandering within a world. Furthermore, we convert popular few-shot learning approaches into online versions and we also propose a new contextual prototypical memory model that can make use of spatiotemporal contextual information from the recent past.

 

Bayesian Few-Shot Classification With One-Vs-Each Polya-Gamma Augmented Gaussian Processes
Jake Snell University of Toronto, Richard Zemel Columbia University

Few-shot classification (FSC), the task of adapting a classifier to unseen classes given a small labeled dataset, is an important step on the path toward human-like machine learning. Bayesian methods are well-suited to tackling the fundamental issue of overfitting in the few-shot scenario because they allow practitioners to specify prior beliefs and update those beliefs in light of observed data. Contemporary approaches to Bayesian few-shot classification maintain a posterior distribution over model parameters, which is slow and requires storage that scales with model size. Instead, we propose a Gaussian process classifier based on a novel combination of Pólya-Gamma augmentation and the one-vs-each softmax approximation that allows us to efficiently marginalize over functions rather than model parameters. We demonstrate improved accuracy and uncertainty quantification on both standard few-shot classification benchmarks and few-shot domain transfer tasks.

 

Theoretical Bounds On Estimation Error For Meta-Learning
James Lucas University of Toronto, Mengye Ren University of Toronto, Irene Kameni African Master for Mathematical Sciences, Toni Pitassi Columbia University, Richard Zemel Columbia University

Machine learning models have traditionally been developed under the assumption that the training and test distributions match exactly. However, recent success in few-shot learning and related problems are encouraging signs that these models can be adapted to more realistic settings where train and test distributions differ. Unfortunately, there is severely limited theoretical support for these algorithms and little is known about the difficulty of these problems. In this work, we provide novel information-theoretic lower-bounds on minimax rates of convergence for algorithms that are trained on data from multiple sources and tested on novel data. Our bounds depend intuitively on the information shared between sources of data, and characterize the difficulty of learning in this setting for arbitrary algorithms. We demonstrate these bounds on a hierarchical Bayesian model of meta-learning, computing both upper and lower bounds on parameter estimation via maximum-a-posteriori inference.

 

A PAC-Bayesian Approach To Generalization Bounds For Graph Neural Networks
Renjie Liao University of Toronto, Raquel Urtasun University of Toronto, Richard Zemel Columbia University

In this paper, we derive generalization bounds for the two primary classes of graph neural networks (GNNs), namely graph convolutional networks (GCNs) and message passing GNNs (MPGNNs), via a PAC-Bayesian approach. Our result reveals that the maximum node degree and spectral norm of the weights govern the generalization bounds of both models. We also show that our bound for GCNs is a natural generalization of the results developed in arXiv:1707.09564v2 [cs.LG] for fully-connected and convolutional neural networks. For message passing GNNs, our PAC-Bayes bound improves over the Rademacher complexity based bound in arXiv:2002.06157v1 [cs.LG], showing a tighter dependency on the maximum node degree and the maximum hidden dimension. The key ingredients of our proofs are a perturbation analysis of GNNs and the generalization of PAC-Bayes analysis to non-homogeneous GNNs. We perform an empirical study on several real-world graph datasets and verify that our PAC-Bayes bound is tighter than others.